We shoud use core id bits instead of max cores, in case later with AMD
downcores Quad core Opteron.

[ tglx: arch/x86 adaptation ]
Signed-off-by: NYinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>